The smell of freshly cut canvas of green, dew from the grass wetting your cleats, leather and the crack of the bat. It's that time again, Baseball season. Still we see conditioning programs focusing on the external rotators (ER) of the shoudler (supraspinatus, infraspinatus, teres minor). If you've been in baseball long enough you realize that the ERs of the shoulder do not perform external rotation of the humerus while in the acceleration phase of the pitching motion. The importance of the ERs come into play in deceleration but only a fraction of the percentage. The majority of the deceleration comes form the opposite low back, hip and leg. See Serape Effect.
There is little need to train the ERs to concentrically contract. The emphasis should be on teaching the entire body to share the responsibility of deceleration in order to protect the shoulder.